Style-based content—devices, panels, plumbing fittings, schematic symbols, and multi-view parts (MvParts)—are multi-view blocks (MvBlocks) that have smart connectors that enable them to connect intelligently to form systems. An MvBlock is a custom object that can have different appearances in different view directions. To define the appearance (or view) of style-based content, you assign a pre-drawn block to a specified view in the style definition.
The number and types of blocks that you need depend on your requirements. For a schematic symbol style, typically you can create one 2D block to represent the symbol in a plan view. If you need to create isometric drawings, you can use this block to generate additional blocks for the 12 isometric views (that represent the 12 isometric view directions and orientations).
For other types of style-based content, you need to create the 2D and 3D blocks required to represent the object in plan views and in model views. For example, a plumbing fitting style might require only a 2D block to represent the fitting in a plan view. Similarly, a device style might require a 2D block to symbolically represent the device in a plan view, but—if you need to create sections and elevations that display devices in actual size—the device style will also require an MvBlock for use in a model view (and in other view directions such as Front and Left).
For an introduction to orthographic and isometric views, see Orthographic and Isometric Views of Style-Based Content.